A conservative advocacy organization that keeps its donors secret says it's spending $1 million on a TV ad touting U.S. Sen. Pat Toomey's legislation that's designed to prevent predators from getting jobs in schools. (Mobile users: Scroll down for full story.)

The 10-day election-year ad starts Thursday statewide in Pennsylvania. It comes amid Democrats' criticism of a Senate Republican stance against considering a nominee by President Barack Obama to fill a Supreme Court vacancy.

Toomey, a Republican, is running for a second term in November's election.

The Washington, D.C.-based group, One Nation, isn't required by federal law to disclose its donors because it's organized as a "social welfare" group. It has been airing ads in support of Republican lawmakers.

It's the second time in a week that a conservative organization that shields its donors aired a pro-Toomey TV ad.

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